Ron Buescher, Luke Howard, and Pat Dexter
Teddy Morelock*, Luke Howard, and J. Brad Murphy
Spinach (Spinacia oleracea L.) is a highly nutritious leafy green vegetable that contains high levels of vitamins A, C, E and folate as well as minerals such as iron and calcium. Spinach is high in carotenoids, specifically lutein and β-carotene. Spinach has also been shown to have high ORAC (oxygen radical absorbency capacity) values and to have a high total flavonoids content (100 mg·kg-1). Leaves were collected from 11 commercial cultivars and 15 advanced breeding lines which were grown at the Univ. of Arkansas vegetable substation near Kibler, Arkansas. Samples were placed in polyethylene bags in ice chests and transported to the Univ. of Arkansas within 2 hours and samples were stored at -20 °C until analysis were performed. Both growing season and genotype had an effect on both ORAC and total phenolics. Over-winter spinach, which is planted in the fall and harvested in the spring, had higher total phenolics as well as higher ORAC than fall-planted fall-harvested spinach. Univ. of Arkansas breeding lines had higher average levels of total phenolics and ORAC than commercial cultivars. These data indicate that it should be possible to breed for higher antioxidant capacity in spinach. In a separate study involving the same cultivars wide variation in lutein content was observed with the cultivars F380 and Fallgreen having the highest levels. Data indicate wide variation in lutein and that breeding for increased lutein content is possible.
Penelope Perkins-Veazie, Brent Black, Ingrid Fordham, and Luke Howard
Autumn olive (Elaeagnus umbellata) is a small red berry that grows on shrubs from Maine to Alabama. This plant originated in China and was introduced to the U.S. in the late 1800s for erosion control. About 20% of the berry' fresh weight is in its single, large seed. The berries of Autumn olive are extremely rich in lycopene (30–50 mg/100 g). The berries are astringent, indicating that fruit may be high in phenolic compounds as well as carotenoids. There has been great interest in producing the plants in domesticated plantings, and in using the fruit as a natural source of lycopene.
This study was done to determine the relative contents of lycopene and phenolics among selections and varieties of autumn olive. The lycopene content of six selections and varieties was 30 to 55 mg·g–1. The lycopene content of berries did not increase after 4 days storage at 25 °C followed by 2 days at 5 °C. Autumn olives are high in soluble solids content (11% to 17%), and relatively high in acidity (1.7% to 5.5% citric acid). The astringent flavor of the berries may be due to the high total phenolic content (1700 mg·kg–1 chlorogenic acid equivalents). The berries were found to be high in flavanols and hydroxybenzoic acids (33 rutin and 31 gallic acid mg·kg–1 equivalents), while the seeds were high in hydroxycinnamic acids and extremely high in hydroxybenzoic acids (35 chlorogenic acid and 184 gallic acid mg·kg–1 equivalents).
Mohamed S. Al-Saikhan, Luke R. Howard, and J. Creighton Miller Jr.
Two varieties of yellow flesh (Granola and Yukon Gold) and two white flesh (Viking and Russet Norkotah) potatoes were grown near Springlake, Texas in the summer of 1992. Varieties were investigated for their antioxidant activity and total phenolic content. Varieties were significantly different in antioxidant activity and total phenolic content (P = 0.0001). Granola had the highest antioxidant activity and Russet Norkotah the highest total phenolic content, while Yukon Gold had the lowest antioxidant activity and total phenolic content. Further study was conducted on tuber parts (distal end, center, and stem end) and among sections within each tuber part. Differences were slight among tuber parts in antioxidant activity, but significant in total phenolic content. Moreover, the differences were slight among the three sections for antioxidant activity and total phenolic content, while the fourth section containing the skin (epidermal tissue) had the highest antioxidant activity and total phenolic content.
Mohamed S. Al-Saikhan, Luke R. Howard, and J. Creighton Miller Jr.
The influence of variety and location on flesh color was examined using Texas and Colorado grown tubers from ten yellow flesh and two white flesh potato varieties. Flesh color was determined using a Hunter Colorimeter, which gives three readings, L* (lightness to darkness), a* (green-red index) and b* (blue-yellow index) Three readings were taken from each tuber at the distal end, center, and stem end. There were significant differences in color among varieties grown in each location for L*, and at both locations, the center was darker. The distal end had the highest chroma and hue angle values at both location. Significant differences were found between the same variety grown in both locations for L*, chroma, and hue. Chroma and hue were greater in Texas grow tubers which indicated more redness. Lower mean hue angle values indicated that Texas tubers were more red, whereas Colorado tubers were yellow. Higher mean chroma values indicated that Texas grown tubers were redder than Colorado grown tubers. L*, chroma, and hue angle are the most useful quantitative measurements.
Derek W. Barchenger, John R. Clark, Renee T. Threlfall, Luke R. Howard, and Cindi R. Brownmiller
Muscadine grapes (Vitis rotundifolia Michx.) are native to the southeastern United States and have potential for greater fresh-market sales if postharvest storage can be improved, but limited information is available on postharvest storability. In 2012 and 2013, physiochemical and storability attributes were measured in 17 muscadine genotypes (selections and cultivars) from the muscadine breeding program at the University of Arkansas or commercial cultivars. The postharvest and physiochemical attributes of the muscadines were measured at harvest and during storage for 3 weeks at 2 °C. Nutraceutical compounds were measured initially after harvest. As a result of extreme differences in weather in 2012 and 2013, the data were analyzed by year. Genotypes significantly affected storage attributes [weight loss (%), and unmarketable berries (%)] and physiochemical attributes such as penetration force (force to penetrate berry skin), titratable acidity (TA), pH, soluble solids (%), berry color (L*, chroma, and hue) as well as the nutraceutical compounds. The postharvest attributes of weight loss and unmarketable berries and the physiochemical attribute of penetration force were significantly affected by postharvest storage, but berry composition attributes remained fairly constant during storage. Overall, University of Arkansas selections AM 04, AM 26, AM 28, and the cultivar Southern Jewel had the highest potential for postharvest storage, whereas the genotypes AM 01, AM 15, AM 18, and ‘Nesbitt’ had the least potential. Genotypes AM 03, AM 04, AM 27, and ‘Ison’ had the highest nutraceutical contents [total anthocyanins, total phenolics, total flavonols, resveratrol, and oxygen radical absorbance capacity (ORAC)], whereas AM 18, AM 28, ‘Supreme’, and ‘Tara’ had the lowest contents. Postharvest storage potential, berry composition, berry color, and nutraceutical content were genotype-specific, but commercially viable genotypes were identified that can provide genetic material for breeding programs and postharvest evaluation protocol for commercial use.
Daniela M. Segantini, Renee T. Threlfall, John R. Clark, Luke R. Howard, and Cindi R. Brownmiller
Fresh-market blackberries (Rubus subgenus Rubus Watson) have a growing global market, with continued release of cultivars to meet demand for consumer-quality fruit. The release of primocane-fruiting blackberry plants that produce crops on both floricanes and primocanes has expanded blackberry production. This study investigated the physiochemical attributes of fresh-market blackberries harvested from two cane types (floricane and primocane) from four primocane genotypes (APF-238, APF-268, ‘Prime-Ark® 45’, and ‘Prime-Ark® Traveler’) grown at the University of Arkansas Fruit Research Station, Clarksville in 2015 and 2016. Year-to-year differences were evident as blackberries harvested in 2016 were smaller (6 g) and less acidic (0.7% titratable acidity) than berries harvested in 2015 (8 g berries with 0.9% titratable acidity); however, soluble solids in each year were similar (≈10.2%). Differences in genotypes were also a factor. ‘Prime-Ark® Traveler’ (2015) and APF-268 (2016) had the highest berry firmness (7.8–8.3 N). In both years, APF-238 had the lowest firmness (5.7–6.0 N), highest isocitric acid (0.8–1.1 g/100 g), and highest total anthocyanins (239–353 mg/100 g). Floricane fruit harvested from ‘Prime-Ark® Traveler’ had the highest berry weights (8.3–10.4 g) in both years. Blackberries harvested from primocanes were wider (21.3–22.9 mm), had higher soluble solids (11.6% to 12.6%), and had lower titratable acidity (0.6%) when compared with floricane fruit in both years. Major year-to-year differences were found for several variables in this study, indicating that environmental effects can be substantial and growers should be aware of this influence on berries harvested from the different cane types. Evaluation of quality properties of floricane and primocane fruit of primocane plants in other locations would be valuable, particularly from areas where commercial blackberry production is established.
Derek W. Barchenger, John R. Clark, Renee T. Threlfall, Luke R. Howard, and Cindi R. Brownmiller
A major limiting factor in fresh-market muscadine grape (Vitis rotundifolia Michx.) commercialization is fruit deterioration during storage. Research on table grapes has shown that field fungicide applications increase storability, but little is known of their effect on muscadines. The effect of field applications of fungicides on physicochemical attributes during postharvest storage and nutraceutical content at date of harvest was evaluated on five muscadine cultivars (Nesbitt, Southern Jewel, Summit, Supreme, and Tara) and four breeding selections from the University of Arkansas Fruit Breeding Program in 2012 and 2013. There were two field treatments (no fungicide and fungicide). For the fungicide treatment, alternating applications of two fungicides were applied to the vine at 14-day intervals during berry maturation. Fruit was harvested and physicochemical attributes including berry volume, titratable acidity (TA), pH, soluble solids (%), color (L, chroma, and hue), firmness (force to penetrate berry skins and flesh), storage weight loss (%), and unmarketable fruit (%) were evaluated every 7 days for 3 weeks. Whole muscadine berries were analyzed for nutraceutical content only for the date of harvest. As a result of less decay, less weight loss, and greater firmness during storage, AM 27, ‘Southern Jewel’, and ‘Supreme’ had the highest potential for postharvest storage, whereas AM 01, AM 15, and ‘Tara’ had the least potential. Nutraceutical content varied by genotypes; overall AM 27 had the highest nutraceutical content [sum of anthocyanins, total phenolics, flavonols, resveratrol, and oxygen radical absorbane capacity (ORAC)], whereas ‘Supreme’ and AM 28 had the lowest. Total anthocyanins were only found in the black genotypes and total phenolics and resveratrol were unaffected by fungicide treatment. Total ellagitannins varied among the fungicide treatments. Total flavonols were generally greater in the no fungicide treatments, whereas ORAC was generally greater with fungicide treatments. Year of study and genotype were determined to be major contributors as sources of variation. Although field fungicide applications did not affect all postharvest attributes and nutraceutical components, differences among genotypes and fungicide treatments did occur.
Mitchell E. Armour, Margaret Worthington, John R. Clark, Renee T. Threlfall, and Luke Howard
Red drupelet reversion (RDR) is a postharvest disorder of blackberries (Rubus L. subgenus Rubus Watson) in which fully black drupelets revert to red after harvest. This disorder can negatively impact consumer perception of fresh-market blackberries. The cause of RDR is hypothesized to be related to intracellular damage sustained because of mechanical and environmental stress during and after harvest. Cultivars differ in susceptibility to this disorder; and cultural factors, including nitrogen rate, harvest and shipping practices, and climate during harvest, influence RDR severity. In this 2-year study, seven genotypes (cultivars and advanced selections) developed in the University of Arkansas System Division of Agriculture (UA) blackberry breeding program, with a range of fruit textures, were evaluated to determine whether firmness was correlated with RDR. In addition, fruit was harvested at four different times (7:00 am, 10:00 am, 1:00 pm, and 4:00 pm) to investigate whether harvest time influences RDR. All seven genotypes were harvested at the four times on two harvest dates per year and evaluated for RDR and firmness after 1 week of cold storage (5 °C). Fruit harvested early in the day had less RDR, with 7:00 am harvests having the least RDR in both years. Significant genotypic differences in RDR and fruit firmness were found in each year. Firmness was negatively correlated with RDR in 2018 and 2019. These results indicate that growers may be able to reduce the prevalence of RDR by choosing cultivars with firm fruit texture and harvesting early in the day.
Renee T. Threlfall, Olivia S. Hines, John R. Clark, Luke R. Howard, Cindi R. Brownmiller, Daniela M. Segantini, and Lydia J.R. Lawless
Blackberries (Rubus subgenus Rubus Watson) are grown worldwide for commercial fresh markets. Physiochemical and sensory attributes were evaluated on fresh fruit of five blackberry cultivars (Natchez, Osage, Ouachita, Prime-Ark® 45, and Prime-Ark® Traveler) and six advanced breeding selections from the University of Arkansas Fruit Breeding Program. The physiochemical attributes of blackberries were within a commercially acceptable range (soluble solids = 8% to 11%, pH = 3.0–3.6, titratable acidity = 0.7% to 1.4%, berry weight = 6 to 14 g, drupelets/berry = 50 to 150, and pyrenes/berry = 51 to 115). ‘Natchez’ had the highest berry weight, berry length, drupelets/berry, and pyrenes/berry, whereas A-2453 was the lowest for these attributes. The highest nutraceutical levels were found in ‘Osage’ (total flavonols and total anthocyanins), A-2434 (total ellagitannins) and A-2453 (total phenolics). A trained descriptive sensory panel (n = 9) evaluated fresh blackberry attributes for appearance, basic tastes, feeling factors, aromatics, and texture using a 15-point scale (0 = less of the attribute; 15 = more of the attribute in terms of intensity). The descriptive panel identified ‘Natchez’ as having the largest descriptive size of berry with the highest overall aromatics and A-2453 as the smallest, glossiest, and firmest. Although A-2491 had the highest soluble solids, the descriptive panelists could not differentiate sweetness among the genotypes, but found A-2491 the least sour. A consumer sensory panel (n = 74) evaluated appearance, flavor, and texture attributes of blackberries on a 9-point verbal hedonic liking scale (1 = extremely dislike; 9 = like extremely) and 5-point just about right (JAR) scale (1 = not nearly enough; 3 = JAR; 5 = much too much). In terms of overall impression and overall flavor, A-2491 and ‘Prime-Ark® Traveler’ had the highest liking; average attributes for these blackberries were a berry weight of 9.1 g, soluble solids of 10.0%, titratable acidity of 0.95%, and a soluble solids/titratable acid ratio of 11.9. ‘Prime-Ark® Traveler’ also had the highest liking for appearance and berry size. A-2453, the glossiest berry, had the highest liking for berry color. Consumer panelists liked the firmness of the blackberries including those that were very firm, such as A-2453, but did not indicate differences in liking among genotypes. Consumers found the size of ‘Ouachita’, ‘Prime-Ark® Traveler’, and ‘Prime-Ark® 45’ (berry weight ≈8.3 g) JAR, but ‘Natchez’ (14.3 g) too large. Consumers found the sweetness and sourness of A-2491 JAR. Consumer overall impression and flavor of blackberries were positively correlated to consumer liking of berry shape and color and negatively correlated to the descriptive attributes for sourness, bitterness, green/unripe aromatic, and amount of seeds. Consumer liking of appearance was positively correlated with consumer liking of berry size, shape, color, and descriptive uniformity of color and glossiness. To produce a commercially marketed fresh-market blackberry, there are many characteristics that are important, but our data for these genotypes suggest that a desired blackberry should have a berry weight of 8–10 g, soluble solids of 9% to 11%, titratable acidity of 0.9% to 1%, and a soluble solids/titratable acid ratio of 10 to 13. However, optimum sugar and acidity levels require more investigation including other factors in flavor and aromatics. Evaluating the physiochemical and sensory attributes of fresh fruit is an important tool that can be used to determine commercial potential for selections and cultivars.